National Fire Safety Criterion (NFSC) in Korea is regulations which prescribe various specifications with regard to fire safety facilities. For example, NFSC rule 203 fire safety standard for automated fire detection facilities regulates mandatory conditions for an automated fire detection facility of a building.
According to NFSC rule 203, a detector is defined as a device capable of detecting fire by itself to send alarm to a control panel, and a transmitter is defined as a device for a person who recognizes a fire to report. P type class 1 transmitter, among various transmitters, has a push button and a lamp for the person who activates it to ascertain its operation, with telephone circuitry between the transmitter and the fire alarm control panel, while P type class 2 transmitter has a push button without telephone function. Fire alarm control panels are classified as P type, R type, M type, GP type, GR type. R type and GR type control panels are capable of receiving respective alarm signals from a plurality of detectors or transmitters (for more than 100 pieces of repeaters), which are equivalent of more than 100 repeaters, and of notifying the concerned authorities. R type and GR type control panels are needed to easily identify installed location of the activated detectors or transmitters, therefore each of detectors or transmitters may have its own identifier. For a large scale building or complex, it is irrational to directly connect thousands of detectors or transmitters to a central fire alarm control panel, such that the regulation requires a repeater to receive alarm signals (including identifiers) from each of detectors or transmitters then to relay the alarm signals to the fire alarm control panel or another repeater.
Repeater is a device which delivers signals caused by activation of a detector or a transmitter to a fire alarm control panel, and control signals for smoke ventilation system or varying fire extinguishing facilities. Thus, repeaters necessarily have input channel from a fire alarm control panel and output channel to the fire alarm control panel.
Conventional R type and GR type fire alarm control system utilizes RS 485 or RS 422 specification for connecting several repeaters to an R/GR type fire alarm control panel. RS 485/422 specification may provide differential communication network, within 1 km length more or less, for up to 127 or 255 repeaters in case of multi-drop connections. Generally, one R/GR type fire alarm control system may cover one moderate building. But, conventional R/GR type fire alarm control system is not suitable to construct an integrated fire control system for a residence complex or a college campus, as well as a skyscraper.
Actually, fire surveillance systems constructed with RS485/422 wiring suffer frequent false alarms and malfunctions, causing janitors of the buildings to turn off and neglect the surveillance systems. Owing to habitual constructions of poorly performing fire surveillance system, the system is practically considered as a formal requirement to get a permit on the completion of a building.